Skin inflammation in Atopic Dermatitis (AD) patients includes dendritic cells, mast cells and T cells. Evidence for the function of several T helper subsets in AD exists both from patient samples and from mouse models. There is clearly a genetic component in disease; family history of allergy is one of the strongest predictors of AD, and mutations in the filaggrin (FLG) gene, a component of the Epidermal Differentiation Complex (EDC), have emerged as a predisposing factor for the development of AD. IL-4 and IL-13 promote atopic responses and decrease expression of a number of EDC genes, which are critical for barrier function. One of the primary questions that remain unanswered is whether the defect leading to AD is in the skin, in the atopic immune system, or whether disease requires defects in both systems. Central to answering this question is an understanding of how the immune system and the skin, particularly keratinocytes, interact at the molecular level. The overall goal of this Project is to define the interactions of cytokines that promote the development of atopic inflammation on keratinocyte gene expression and function, with the long-term goal of finding pathways that could be targeted for treatment of disease. Our hypothesis is that pro-allergic cytokines change the biology of keratinocytes and alter barrier function, facilitating increased allergen exposure. This hypothesis will be examined in two Aims that will examine the interactions of filaggrin mutations with increased Th2 immunity in a mouse model system, and define the function of STAT6 in regulating keratinocyte gene expression. Together, these studies will provide a detailed understanding of the effects of cytokines produced during allergic inflammation on skin barrier function.